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Employee Share-Based Incentive Compensation Plans (Tables) - White Mountains | 9 Months Ended
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Sep. 30, 2018
Share-based compensation arrangement by share-based payment award |
Summary of performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan | The following table presents the performance share activity for the three and nine months ended September 30, 2018 and 2017 for performance shares granted under the WTM Incentive Plan:
|  | Three Months Ended September 30, |  | Nine Months Ended September 30,
|  | 2018 |  | 2017 |  | 2018 |  | 2017
Millions, except share amounts |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense |  | Target Performance Shares Outstanding |  | Accrued Expense
Beginning of period |  | 40,616 |  |  | $ | 27.2 |  |  | 50,575 |  |  | $ | 31.2 |  |  | 50,515 |  |  | $ | 45.8 |  |  | 80,353 |  |  | $ | 42.4 |
Shares paid (1) |  | — |  |  | — |  |  | — |  |  | — |  |  | (23,186 | ) |  | (28.4 | ) |  | (30,838 | ) |  | (21.6 | )
New grants |  | — |  |  | — |  |  | — |  |  | — |  |  | 14,105 |  |  | — |  |  | 17,510 |  |  | — |
Forfeitures and cancellations(2) |  | — |  |  | (.1 | ) |  | (256 | ) |  | (.4 | ) |  | (818 | ) |  | .1 |  |  | (16,706 | ) |  | (9.4 | )
Expense recognized |  | — |  |  | 7.8 |  |  | — |  |  | 7.0 |  |  | — |  |  | 17.4 |  |  | — |  |  | 26.4 |
End of period(3) |  | 40,616 |  |  | $ | 34.9 |  |  | 50,319 |  |  | $ | 37.8 |  |  | 40,616 |  |  | $ | 34.9 |  |  | 50,319 |  |  | $ | 37.8 |
(1) WTM performance share payments in 2018 for the 2015-2017 performance cycle, which were paid in March 2018, ranged from 145% to 147% of target. WTM performance share payments in 2017 for the 2014-2016 performance cycle, which were paid in March 2017, ranged from 34% to 76% of target. (2) Amounts include changes in assumed forfeitures, as required under GAAP. (3) Outstanding performance share awards as of September 30, 2017 excludes 2,195 performance share awards granted to employees of Sirius Group.
Share-based Compensation, Performance Shares Award Outstanding Activity | The following table presents performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan at September 30, 2018 for each performance cycle:
Millions, except share amounts |  | Target Performance Shares Outstanding |  | Accrued Expense
Performance cycle: |  |  |  |  |  |
2016 – 2018 |  | 13,715 |  |  | $ | 18.9 |
2017 – 2019 |  | 14,070 |  |  | 13.3 |
2018 – 2020 |  | 13,450 |  |  | 3.2 |
Sub-total |  | 41,235 |  |  | 35.4 |
Assumed forfeitures |  | (619 | ) |  | (.5 | )
September 30, 2018 |  | 40,616 |  |  | $ | 34.9 |
Summary of restricted shares activity | The following table presents the unrecognized compensation cost associated with the outstanding restricted share awards for the three and nine months ended September 30, 2018 and 2017:
|  | Three Months Ended September 30, |  | Nine Months Ended September 30,
|  | 2018 |  | 2017 |  | 2018 |  | 2017
Millions, except share amounts |  | Restricted Shares |  | Unamortized Issue Date Fair Value |  | Restricted Shares |  | Unamortized Issue Date Fair Value |  | Restricted Shares |  | Unamortized Issue Date Fair Value |  | Restricted Shares |  | Unamortized Issue Date Fair Value
Non-vested, |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning of period |  | 41,510 |  |  | $ | 19.0 |  |  | 53,815 |  |  | $ | 23.5 |  |  | 53,755 |  |  | $ | 14.3 |  |  | 70,620 |  |  | $ | 19.7 |
Issued |  | — |  |  | — |  |  | — |  |  | — |  |  | 14,105 |  |  | 11.4 |  |  | 17,785 |  |  | 16.7 |
Vested |  | — |  |  | — |  |  | (260 | ) |  | — |  |  | (25,381 | ) |  | — |  |  | (28,846 | ) |  | — |
Forfeited |  | — |  |  | — |  |  | — |  |  | — |  |  | (969 | ) |  | (.2 | ) |  | (6,004 | ) |  | (3.5 | )
Expense recognized |  | — |  |  | (3.2 | ) |  | — |  |  | (3.8 | ) |  | — |  |  | (9.7 | ) |  | — |  |  | (13.2 | )
End of period (1) |  | 41,510 |  |  | $ | 15.8 |  |  | 53,555 |  |  | $ | 19.7 |  |  | 41,510 |  |  | $ | 15.8 |  |  | 53,555 |  |  | $ | 19.7 |
(1) Restricted share awards outstanding as of September 30, 2017 includes 2,195 restricted shares issued to employees of Sirius Group, which was accounted for as discontinued operations.

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